1. Field of the Invention
The present invention relates to lighting fixtures (hereafter referred to as xe2x80x9cluminairesxe2x80x9d) which provide up-lighting, i.e. upwardly directed light. More particularly, the invention relates to luminaires of this type in which the upwardly directed light illuminates the ceiling extremely evenly.
The invention will be described in the context of a pendant type fixture, i.e., one which hangs from a ceiling, but the invention is also applicable to luminaires which are free-standing or mounted on tables, furniture or other raised horizontal surfaces, and to wall mounted units (e.g. sconces), or even angled down from a ceiling for wall illumination.
Luminaires according to the invention are capable of providing optional down-lighting, i.e. downwardly directed light components, as well as up-lighting.
2. Description of the Related Art
Luminaires which provide up-lighting are known. In such devices, important design considerations, apart from the overall aesthetics of the fixture, include both the extent and the uniformity of illumination. In some known devices, the latter consideration is not adequately addressed, and the light source within the fixture is mirrored on the ceiling, resulting in a relative xe2x80x9chot spotxe2x80x9d in ceiling illumination. Of course, care must also be taken that technical requirements like uniformity of light distribution are not met at the expense of aesthetic considerations.
In known pendant fixtures which use elongated light sources like fluorescent tubes, achieving a uniform lighting pattern can sometimes be difficult. In particular, tubular lamps tend to project a bright line of light onto the ceiling running longitudinally directly above the fixture, with an xe2x80x9chourglassxe2x80x9d pattern extending to the sides. Covering the lamp with a translucent diffuser or a louver array have been used to improve the uniformity of the lighting pattern, but these have had the effect of reducing the amount of upwardly directed light.
The problem can be particularly acute with tapered fixtures (i.e., fixtures in which the cross-section varies along the length) due to edge effects. Conventional fixtures are therefore usually linear, i.e., with no cross-sectional variation along the length, despite the esthetic appeal of tapered designs.
The present invention provides desirable uniformity of up-light distribution for elongated tapered luminaires that use tubular light sources, like linear fluorescent lamps, tubular double ended halogen lamps or the like, without unacceptable reduction in light output, or compromise of aesthetic considerations.
According to a first aspect of the invention, there is provided a lighting fixture comprised of an elongated tapered body having an axis of elongation extending in a first direction, the body including a cavity having an opening therein, mounting means for mounting the fixture with the cavity opening oriented toward a surface to be illuminated, lamp mounting means for positioning a lamp in the cavity so it extends in the first direction with the lamp exposed to illuminate the surface, and means for interacting with light emitted from the lamp so that the surface is illuminated a substantially uniform pattern extending in the first direction and transversely of the first direction.
According to a second aspect of the invention, there is provided a lighting fixture comprised of an elongated tapered body having an axis of elongation extending in a first direction, the body including a cavity having an opening therein, a fixture mounting assembly for positioning the fixture with the cavity opening oriented to provide lighting directed toward a surface, a lamp mounting assembly that positions a lamp in the cavity so it extends in the first direction, with the lamp exposed to provide illumination toward the surface, and a louver assembly including a plurality of louvers spaced along the axis of elongation, the louvers extending outward from the body cavity opening and transversely of the axis of elongation, the louver assembly being operative to direct light toward the surface to be illuminated in a substantially uniform pattern extending both in the first direction and transversely of the first direction.
Broadly stated, the desired uniform illumination according to the second aspect of the invention is achieved by provision of a louver assembly in which the louvers project from a cavity opening in the fixture body toward the surface being illuminated. The louvers are preferably of different sizes so that the louver assembly has a varying cross-section and profile from end to end.
In one embodiment according to the second aspect of the invention, the louvers may be partial disks having semi-circular perimeters with the disks becoming progressively smaller from the center of the fixture to the ends. The profile of the louvers preferably follows a smooth curve. The body is correspondingly tapered, so that when viewed from the side, the fixture appears to be ellipsoidal. This design is effective in producing a uniform light distribution without compromising the aesthetics of the luminaire.
In another embodiment according to the second aspect of the invention, the louvers are partial disks having semi-elliptical perimeters, and having their minor axes extending vertically. The minor axes of the louvers become progressively shorter from the middle of the fixture toward the ends. Again, the profile of the louvers may follow a smooth curve which matches that of the body so the fixture appears ellipsoidal when viewed from the side. This design is also effective in producing a uniform light distribution without compromising aesthetics. In this design, light is more broadly distributed i.e., transversely of the direction of elongation, than with the previous embodiment.
In a further embodiment according to the second aspect of the invention, the louvers are partial disks having semi-elliptical perimeters, with their major axes extending vertically. Again, the louvers vary in size progressively with the largest ones at the middle of the fixture and the smallest ones at the ends. This design produces a narrower band of illumination transversely of the fixture axis than in the case of the two embodiments previously described.
Other specific louver cross-sections may also be employed. The louvers may be parabolic, or even polygonal, to tailor the light distribution to a particular ceiling curvature, or for aesthetic effects.
According to a third aspect of the invention, there is provided a lighting fixture as described in connection with the first and second aspects, in which the surface to be illuminated is a ceiling. In a first embodiment according to the third aspect, the fixture mounting assembly includes members spaced along the fixture that extend upwardly for attaching the fixture to a ceiling. In a second embodiment according to the third aspect, the fixture mounting assembly includes members spaced along the fixture that extend downwardly for attaching the fixture to a surface below a ceiling being illuminated, such as a top surface of a kitchen island. In a variant of the second embodiment the spaced members may be attached to a base so the fixture may be free-standing.
In a further variant of the second embodiment, the spaced members may be attached to the top or to one side of the fixture to provide cantilever support.
According to a fourth aspect of the invention, there is provided a lighting fixture as described in connection with the first and second aspects, in which the surface to be illuminated is a wall, and the fixture is mounted on the wall being illuminated, or on a ceiling and aimed toward the wall.
According to one feature of the invention common to all aspects thereof, the louver assemblies are comprised of one or more integral structures installable and removable as complete units, whereby it is possible with a single overall fixture design, to control illumination for different lighting environments by choice of specific louver configurations.
According to a further feature of the invention common to all aspects, improved uniformity of illumination can be achieved by use of transparent or translucent, rather than opaque louvers. This permits the louvers to direct light more efficiently over a wider area of the illuminated surface.
For purposes of this description, the term xe2x80x9ctransparentxe2x80x9d applies to a structure which does not obscure the visible features of an object lying beyond it. The term xe2x80x9ctranslucentxe2x80x9d applies to a structure which emits or passes diffuse light, but obscures objects lying beyond it. The term xe2x80x9copaquexe2x80x9d applies to an object which is impenetrable to light.
Translucency can be achieved by selection of material or a treatment like sandblasting that produces a textured surface.
According to a yet another feature of the invention, the peripheries of the individual louvers may be transparent and beveled. This produces a controlled refraction of the exiting light rays, and enhances the uniformity of the up-lighting effect. Especially good results are achieved if the sides, i.e., the parallel faces of the louvers are translucent.
For beveled louvers, when the louvers are progressively shorter at the ends of the fixture than in the middle, the center louver or louvers are preferably flat, i.e. not beveled, and the beveled faces on opposite sides of the center face the respective nearest ends of the fixture. Alternatively, the beveled faces on opposite sides of the center may be reversed so they face toward the center of the fixture.
Uniform bevel angles, i.e., relative to the longitudinal axis of the fixture, may be employed on each louver (facing either inward or outward). Alternatively, the bevel angles may increase progressively toward the ends of the fixture, or the angle of individual louvers can be tailored. This permits control of the light distribution pattern in case the illuminated surface is not flat but is curved in some fashion.
An internal reflector may also be provided to further improve the distribution of the illumination.
According to a another feature of the invention, the louvers are attached to an elongated support structure which runs the length of the fixture. The support structure may be one or more rods or a partial tube, e.g., a semi-cylinder, surrounding the lamp and integral with the louvers. In the latter case, the partial tube may be opaque, but is preferably translucent or transparent.
Especially uniform light distribution can be achieved by beveling the tops of the louvers in an embodiment in which the vertical faces of the louvers and the portions of the semi-cylindrical support element between the louvers are translucent.
Other features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.